Only when rpms are between 2500-3500 or somewhere close in that range, it sounds like a belt is slipping (not squeaking), or kind of like a buzzing, something to that nature.....no check engine light, no indication that anything is wrong other than the fact that sometimes I get this weird noise.

It's not consistent. Only seems to happen at lower rpms.

I know I have the secondary air pump sound but that goes away after it warms up, and this sound just started recently...

If anything I've mentioned is a tell-tale sign of something, please let me know...

 

Now it seems to be happening throughout all the RPM ranges, but it doesn't happen in neutral when the engine is revved.....this is driving me crazy. I wish whatever it is would just break so I can figure out what it is.

It's almost like some sort of crackling sound, definitely not just water going through the heater core or some crap like that...

 

Search out a thread by Jon316G and "SSV", maybe the solenoid is chattering? There is other info in that thread that might be of use as well? This is just a pure guess as to what it may be, since you are convinced it's not MIAC.
Probably need to get in there and isolate where the noise is coming from.

 

Secondary air pump only operates on startup until the engine is warm.
It's purpose is to reduce emissions.

It adds air to the exhaust to help bring the catalytic converter up to temperature faster.

 

I'll do a search, just seems unlikely this is the problem as it only seems to happen under a load, and not around any certain RPM. It's making the noise far before the SSV opens up, and MIAC is usually accompanied by a check engine light.

 

You could try disconnecting some belts to see if any pulleys are loose. Before that though, you should check to see if the belts are at the correct tension and alignment. It may be that they are stretched.

 

I purchased some new belts for the hell of it(have yet to install), not sure if the current ones are off alignment/tension, they have been the same since I bought the car....

 

Never known MIAC to throw a CEL.............I understand what you are saying about the SSV, but the thread I mentioned has other possibilities in it as well.

 

You say it doesn't do it in neutral, how about when you push the clutch in? If it goes away then I would suspect the throw out bearing.

 

Assuming its a standard transmission.

 

Unless you are pushing in the clutch the throwout bearing is just idling along doing nothing

Usually throwout bearing failure results in grinding noises when the clutch is pushed in

 

Only does it while accelerating, and gets louder the higher rpms you go. In neutral with the clutch in or out, does nothing.

 

If you have a camera handy or can borrow one that should help people. A belt slipping sound to you could be another sound to another ear.

 

A sound video can help diagnose the problem of the op, but sometimes its not that easy to tell from a video itself, just sayin'.

 

I'll try to get a sound clip together, all I can say for sure now is that it doesn't happen in neutral even when you rev the engine all the way to 9k.

Also the sound increases in frequency and volume the higher RPM you go while in gear, and it seems to be relative to RPM and not speed.

I've read about a dozen MIAC threads, what seems to be different about my problem is that it ONLY happens when the car is under load, and in all RPM ranges.

And it's really odd that it just started happening after 91k miles....

It does however seem to be coming from behind the glove box.